Officials representing Syrian dictator Bashar al-Assad branded the targeted U.S. airstrikes on a pro-government militia that had reportedly violated a “de-confliction zone” a “massacre” and “government terrorism” Friday, while Assad’s patron Russia called the American measure “unacceptable,” Breitbart reported.

“We discussed the massacre that the U.S. aggressor committed yesterday in our country,” Syrian government negotiator Bashar al-Ja’afari said, referring to a conversation with United Nations mediator Staffan de Mistura and referring to the U.S. action as “government terrorism.”

“At every meeting, we would like to remind the attendees that state terrorism is being practiced against our country,” al-Ja’afari alleged, tacitly referencing the isolated American military action, according to the Syrian state-run news agency SANA.

SANA added that al-Ja’afari objected to the enforcing of “de-confliction zones” established by the Astana agreement, a multilateral attempt to establish peace in Syria led by Iran and Russia because “the mechanisms of implementing the agreement have not been set yet.”

The Russian Foreign Ministry also issued a stern condemnation of the American airstrikes on Friday, calling the attack “absolutely unacceptable.”

“Any military actions entailing the aggravation of the situation in Syria certainly influence the course of the political process, especially such actions that were committed against the Syrian armed forces,” Russian Deputy Foreign Minister Gennadiy Gatilov said, according to SANA.

On Thursday, America’s Freedom Fighters reported that American airstrikes hit pro-Assad forces in southern Syria as they were setting up fighting positions in a protected area.

The American strikes were the first against Assad positions since the Pentagon rained 57 Tomahawk missiles on the Shayrat air base near Homs.

But the strikes confirmed Thursday were believed to be the first targeting Syrian personnel. According to the defense official, the coalition strikes targeted pro regime units operating in the vicinity of Al-Tnaf. After a show of force to try to stop the pro regime forces was ignored, the strikes were mounted.

One official says the pro-regime forces had entered a so-called “de-confliction” zone without authorization and were perceived as a threat to U.S.-allied troops there. The officials say the strike was a defensive move to protect U.S. allies. It wasn’t clear if U.S. forces were there.

“The coalition commander assessed the threat and after shows of force didn’t stop the regime forces and those forces refused to move out of the deconfliction zone, the commander on the ground called for the air strike as a matter of force protection,” a senior US defense official told Fox News.

But the attack on forces does not reflect an escalation, the official said.

“We are not increasing our role in the Syrian civil war, but we will defend our troops,” Secretary of Defense James Mattis said of the decision to strike. “And that is a coalition element made up of more than just U.S. troops, and so we will defend ourselves (if) people take aggressive steps against us.”

On Friday, a Syrian military source said the strikes had hit “one of our military points” and caused an unspecified number of deaths. UPI later reported on Friday, citing both Syrian and Russian sources, that the strikes killed at least eight.